To clarify, for anyone in England the rules were changed and wedding suppliers are not included in your guest numbers. So if your max numbers are 15, that's 15 guests PLUS your suppliers. Unless they change things again of course, which wouldn't surprise me!
In terms of making things special, we had 14 people total at our wedding including us. With the money saved by having a smaller guest list we spent more per head on food and drink to ensure there were big portions, lots to go around. Lots of things to nibble on and pick at all day. Lots of canapés and drinks that we knew people liked.
We opted for a dessert table too and included many of our guests favourites from places like the English Cheesecake company, Patisserie Valerie and so on.
We also had "goody bags" for each guest as everyone was staying overnight. These included posh toiletries and personalised thank you for coming notes.
Another thing we had was an "oh shit kit" which included lots of little things people may have forgotten to bring or needed- deodorant, plasters, suncream, paracetemol, breath mints and that kind of thing.
We also had blankets for the evening when things got chilly.
We chose to have a later ceremony too (4pm, with sunset at approx 7pm) so there was no rush in the morning to be ready early. The day didn't drag as there were not countless hours to fill with limited numbers.